PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior cytotoxic chemotherapy for metastatic disease At least 6 months since prior adjuvant chemotherapy No concurrent chemotherapy Endocrine therapy: See Disease Characteristics No prior hormonal therapy for metastatic disease At least 12 months since prior adjuvant antiestrogens No concurrent SERMs or estrogenic or androgenic hormones No other concurrent aromatase inhibitors Radiotherapy: No concurrent radiotherapy except for palliation for bone metastases Surgery: Not specified Other: No prior enrollment in this study At least 30 days since prior investigational drugs No other concurrent investigational drugs Concurrent bisphosphonates for bone metastases allowed